Compressor barrel assembly

ABSTRACT

THE THREE STAGE CENTRIFUGAL COMPRESSOR OF THE PRESENT INVENTION EMPLOYS A ONE-PIECE CAST CASING HAVING A CYLINDRICAL BORE CONTAINING THEREIN A REMOVABLE BARREL ASSEMBLY, WHICH ASSEMBLY COMPRISES THREE DIRECTLY ENGAGING DIAPHRAGMS, THREE DIFFUSORS, THREE SHROUDS AND A ROTOR HAVING THREE IMPELLERS, ALL IN AXIALLY STACKED RELATIONSHIP. ONLY THE THREE DIAPHRAGMS ARE AXIALLY CLAMPED DIRECTLY TO EACH OTHER BY MEANS OF TENSION BOLTS. THE DIFFUSERS AND SHROUDS ARE HELD BY THE DIAPHRAGMS FOR AXIAL FREE PLAY AND BIASED IN ONE AXIAL DIRECTION BY AXIALLY COMPRESSED SEALING O-RINGS AND EFFECTIVE PISTON SURFACES UNDER THE INFLUENCE OF THE FLUID BEING PUMPED. THE END CLOSURE CONTAINING THE BEARINGS AND DRIVE FOR THE OVERHUNG ROTOR HAS A CYLINDRICAL SURFACE FLUSH WITH THE CYLINDRICAL BORE OF THE CASING, WHICH SURFACE IS OVERLAPPED BY THE OUTER CYLINDRICAL SURFACE OF ONE OF THE DIAPHRAGMS TO PROVIDE FOR AXIAL ALIGNMENT. FOUR ENGAGING CYLINDRICAL SURFACES ON THE DIAPHRAGMS FURTHER ASSURE AXIAL ALIGNMENT. FLUID PASSAGES ARE PROVIDED INTEGRALLY CAST IN THE DIAPHRAGMS AND CASING FOR CONDUCTING THE FLUID THROUGHJ INTERCOOLERS, BETWEEN STAGES.

Feb. 20, 1973 K. PlLARczYK COMPRES SOR BARREL AS S EMBLY 5 Sheets-Sheetl Filed June 8, 1.970

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K. PILARCZYK Feb. 20, 1973 COMPRES SOR BARREL AS S EMBLY 5 Sheets-Sheet3 Filed June 8, 1970 Feb. 20, 1973 K. PILARCZYK 3,717,418

COMPRESSOR BARREL ASSEMBLY Filed June 8, 1970 5 Sheets-Sheet 4 K.PILARCZYK Feb. 20, 1973 COMPRES SOR BARREL AS SEMBLY 5 Sheets-Sheet 5Filed June 8, i970 bw e @www ,U n, 0

y @Hmm @d United States Patent O U.S. Cl. 415-104 23 Claims ABSTRACT FTHE DISCLOSURE The three stage centrifugal compressor of the presentinvention employs a one-piece cast casing having a cylindrical borecontaining therein a removable barrel assembly, which assembly comprisesthree directly engaging diaphragms, three ditfusors, three shrouds and arotor having three impellers, all in axially stacked relationship. Onlythe three diaphragms are axially clamped directly to each other by meansof tension bolts. The diffusers and shrouds are held by the diaphragmsfor axial free play and biased in one axial direction by axiallycompressed sealing O-rings and effective piston surfaces under theinuence of the Huid being pumped. The end closure containing thebearings and drive for the overhung rotor has a cylindrical surface ushwith the cylindrical bore of the casing, which surface is overlapped bythe outer cylindrical surface of one of the diaphragms to provide foraxial alignment. Four engaging cylindrical surfaces on the diaphragmsfurther assure axial alignment. Fluid passages are provided integrallycast in the diaphragms and casing for conducting the fluid throughintercoolers, between stages.

BACKGROUND OF THE INVENTION It is known to provide axially removablebarrel assemblies for pumping devices, but these have uusally included alarge number of axially stacked elements, so that there will be arelatively large tolerance accumulation in the axial direction andprovide for increased axial length, as well as complexity. Theseproblems would be even further increased with respect to an open type ofcentrifugal impeller. Further, considerable alignment problems areencountered when an overhung rotor is employed, so that overhung rotorsare normally employed only with a single stage of compression. With theconsiderable axial length of removable barrel assemblies for multi-stageimpellers, the problems of whipping that would be encountered if anoverhung rotor were employed in such devices would be considerable sothat their speed of operation would be quite limited. Further, variouspiping connections are normally employed between stages with a tendencyto further increase the axial extent of any multi-stage device, whichwould further make the use of an overhung rotor more difficult.

The temperature gradients throughout a barrel assembly and casing for amulti-stage compressor are considerable, which will have a great eifectwith respect to expansion upon the various elements, particularlyshrouds and diffusers with respect to open type impellers. Since theshrouds and diffuers are closest to the impellers and most difficult tocool, their temperatures are usually quite high so that their thermalstresses and axial thermal expansion are correspondingly quite high,which will further produce disadvantages with respect to tolerances inthe 3,7l7,4l8 Patented Feb. 20, 1973 axial direction when they areinterposed in the clamping of the barrel assembly.

CROSS-REFERENCING TO= RELATED APPLICATIONS The features of the inventionof this application may be used in combination with the features of theinventions in applicants following related applications of the samefiling date and assignee as the present application, the disclosures ofwhich are incorporated herein in their entirety by reference: VariableCapacity Compressor, Ser. No. 44,263, Compressor Power Recovery, Ser.No. 44,463; Interchangeable Compressor Drive, Ser. No. 44,403;Compressor Base and Intercoolers, Ser. No. 44,034.

SUMMARY OF THE INVENTION It is an object of the present invention toovercome many of the disadvantages as mentioned above and provide acompressor with a relatively small axial extent and diameter, and whichmay use intercoolers without a considerable amount of piping about itscasing. The axial limitations with respect to length are of considerableadvantage in providing a minimum length to the cantilevered portion ofan overhung rotor so that high speed operation may be possible, Thepiping connections between stages are cast into removable diaphragme andone piece casing.

The removable barrel assembly includes a diaphragm, a shroud, adiffuser, and an impeller for each stage, with only the diaphragms beingdirectly clamped to each other and the casing so that toleranceaccumulation in the axial direction will be held to a minimum. Theshrouds and diffusers are stationarily mounted between the diaphragms,with axial free play so that their tolerances in the axial directionwill not pass from one stage to another andl their considerable thermalexpansion will not be an accumulating problem. Means are provided tobias the shrouds and diffusers in one axial direction, and includesealing O-rings compressed in the axial direction and piston surfaces onthe shrouds and ditfusers that will produce a net axial force inresponse to the pressure of the fluid being pumped. In this manner, thebarrel assembly has the advantages of a rigid construction, separatepieces for each barrel element and only three elements axially clampedtogether that would produce a tolerance accumulation for the entirelength of the assembly.

BRIEF DESCRIPTION OF THE DRAWING Further objects, features andadvantages of the present invention will become more clear from thefollowing detailed description of a preferred embodiment of the presentinvention as shown in the attached drawing, in which:

FIG. l is a perspective view of a complete compressor employing thefeatures of the present invention;

FIG. 2 is a schematic flow sheet showing the path of the fluid as itmoves between stages and through the intercoolers;

FIG. 3 is a partial cross-sectional view taken on a vertical planepassing substantially through the axis of rotation of the compressor ofFIG. l;

FIG. 4 is a partial perspective exploded view, with portions cut-away,of the one piece compressor casing and its relationship with the topwall of the intercooler chambers;

FIG. 5 is an enlarged cross-sectional view of the barrel assembly andits relationship to the compressor casing and drive, taken substantiallyin the same plane as FIG. 3;

FIG. 6 is a cross-sectional View taken along line 6-6 in FIG. 4;

FIG. 7 is a cross-sectional View of the casing taken along line 7-7 ofFIG. 4;

FIG. 8 is a cross-sectional view of the casing taken along line 3-8 inFIG. 4;

FIG. 9 is a cross-sectional view of the casing taken along line 9-9 inFIG. 4 and FIG. 5;

FIG. 10 is a cross-sectional View of the casing taken along line 10-10of FIGS. 4 and 5;

FIG. ll is a cross-sectional view of the casing taken along line 11--11of FIGS. 4 and 5; and

FIG. 12 is a cross-sectional View of the casing taken along line 12-12of FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE DRAWING With reference to FIGS. l-3, thecompressor base 1 securely mounts an electric drive motor 2, which hasan output shaft 3 for driving the rotor 4 through gear train 5. The geartrain 5 is mounted within a separate casing 6 that forms the end closurefor the compressor casing 7. The casings 6 and 7 are each cast in onepiece from iron, and the base 1 is Welded sheet steel fabrication. Inletuid is provided for the compressor through an inlet housing S havingmounted therein an inlet valve 9 controlled by a suitable mechanism 10.

Within the base 1, there are two separated intercooler chambers 11 and12 for cooling the fluid between the first and second stages and betweenthe second and third stages, respectively. For the purposes of thepresent invention, these intercooler chambers may be of any constructionand include any type of conventional intercooling equipment, such as aparallel tube waterdluid heat exchanger. A shown in FIG. 2, inlet fluidpasses through the first stage impeller 13, the intercooler chamber 11,the second stage impeller 14, the intercooler chamber 12, and the thirdstage impeller 15.

As somewhat schematically shown in FIG. 3, and more accurately in FIG.4, the cast iron casing 7 is provided with an axial cylindrical bore 16and a planar surface 17, with a plurality of integrally cast passagestherebetween for conducting the tiuid between stages and theintercoolers. Particularly, passage 18 conducts fluid from the firststage output to the intercooler chamber 11, passage 19 conducts fluidfrom the intercooler chamber 11 to the second stage, passage 20 conductsfluid from the second stage to the intercooler chamber 12, and passage21 conducts Huid from the intercooler chamber 12 to the third stage. Thepassages in the top of the intercooler chambers have been given numberscorresponding to those used with respect to the casing 7, but with theaddition of primes. The passages 18', 20' extend directly through thetop plate of the base for discharge directly into the chambers 11 and12, while the return fiuid from the chamber 11, 12 is conductedrespectively, in passages 19', 21 which extend for substantially thefull height of the base 1 between the intercooler chambers 11 and 12.

In FIG. 5, a three stage removable barrel assembly is shown Within thecylindrical bore of the casing 7. The first stage includes a diaphragm22, a shroud 23, a diffuser 24 and the impeller 13; the second stageincludes diaphragm 25, shroud 26, diffuser 27, and impeller 14; and thethird stage includes diaphragm 28, shroud 29, diffuser 30, and impeller1S. Each of the diaphragms is a one piece iron casting, and each of thediffusers and shrouds is a one piece aluminum casting. Each of thediaphragms 22, 25, 28 has an outer cylindrical surface in directengagement with the inner cylindrical bore 16 of the casing 7. The endclosure formed by the gear casing 6 has an adjacent inner cylindricalsurface 31 that is flush with the cylindrical surface 16 of thecompressor casing 7, with the outer cylindrical surface of the diaphragmoverlapping these ush inner cylindrical surfaces to accurately align thegear casing 6 with the barrel assembly for proper positioning of therotor 4. The gear casing 6 determines the positioning of the rotor 4, bymeans of the radial bearing 32 and the combination radial-thrust bearing33 that rotatably mount the rotor 4 in an overhung position. Thesebearings provide the sole rotational support for the cantilever-edrotor. The rotor may be of any rigid type construction, but preferablythe impellers 13, 14, 1S are integrally secured to the rotor shaft, withthe interposition of suitable labyrinth seals as shown.

In assembling the barrel assembly, the various components are assembledoutside the casing and slid from left to right, as viewed in FIG. 5,into the casings 6 and 7. Thereafter, the diaphragms 22, 25, 2S arerigidly secured to the gear casing 6 by means of a plurality of tensionbolts 34. In this manner, the gear casing 6 forms the main axialreference element, with the thrust bearing 33 forming the axial fixedreference point for the rotor 4 and the end face 35 forming the axialreference point for the diaphragms; since the gear casing 6 is of a onepiece cast construction, the axial distance between points 33 and 35 isfixed and may be accurately determined. Thus, tolerance accumulation inthe axial direction will occur only from point 35 to the left, as viewedin FIG. 5, and then only with respect to the three diaphragms 22, 25, 28that are directly clamped to each other.

The shrouds 23, 26, 29 and diffusers 24, 27, 30 radially engage thediaphragms to fix their radial position and axially engage, in only onedirection, the diaphragms to fix their axial position while allowingfree axial play or clearance movement in the opposite axial directionwith respect to the diaphragms. r)This axial free play is taken up bybiasing means including the axially compressed sealing O-rings 36, 37and the piston action of the surface exposed to the pumped fluid on thediffusers and shrouds. More particularly, the O-ring 36 will exert anaxial force to the right, as viewed in FIG. 5, directly upon the shroud23 and therethrough indirectly upon the diffuser 24 to tightly clamp theshroud 23 and diffuser 24 against the diaphragm 28, and the O-ring 37exerts an axial force to the right, as viewed in FIG. 5, directly uponthe shroud 29 and indirectly upon the axial stacked diffuser 30,diffuser 27, and shroud 26. In this manner, any tolerance accumulationas between the shrouds and diffusers is not transferred to thediaphragms. Thus, the advantages of providing separate shrouds andseparate dilfusers with respect to manufacturing procedures, replacementand the like, are provided without also providing the heretoforecorrelated disadvantages of tolerance accumulation. Further, the thermalexpansion of the shrouds and ditfusers will not be transferred to thediaphragms, which is of considerable importance considering theextremely high temperatures encountered immediately adjacent theimpeller and in view of the relatively high thermal expansion of thealuminum, from which the shrouds and diffusers are constructed. Withrespect to the piston biasing action, with reference to FIG. 5, it isseen that the shroud 23 has a considerable surface area facing to theleft that is exposed to the high pressure diffuser outlet of the firststage, which will produce an axial force to the right greater than theaxial force to the left produced by the rightwardly facing area exposedto the high speed low pressure gas moving through the impeller 13 andblades of the diffuser 24; the diffuser 24 has substantially only aleft-hand surface exposed to the pressurized gases to produce a netforce in the righthand direction; analysis of the shroud 29 would besimilar to that of the shroud 23, but with considerable affects obtainedby the left-hand exposure of the shroud 29 t0 the gases within the firststage, to produce a net rightwardly oriented axial force; together, thediffusers Z, 30 have opposed surfaces exposed respectively to the outletgases of the second and third stages, with the higher pressure gases ofthe third stage predominating to produce a net axial force in theright-hand direction; due to the c011- struction of the diaphragm 25,the shroud 26 has only a relatively small piston area exposed to theinlet gases for the second stage and has its full radial area exposed tothe gases passing through the impeller 14 and blades of the diffuser 27so that a net axial force is again produced in the right-hand direction.Wherever needed for purposes of sealing, additional O-rings are providedbetween adjacent surfaces, with many of these O-rings not being shownsince they are conventional, but it being understood that theseadditional sealing O-rings do not contribute to the above-mentionedaxial biasing of the shrouds and diffusers. The axial biasing of thepiston effects and the axially compressed O-rings 36, 37 are in the samerighthand direction to complement each other. Thus, while the compressoris idle and during start-up, the shrouds and diifusers will be biasedinto their proper position by the forces of the O-rings 36, 37, while athigh speeds, the piston effect will predominate.

From FIG. 5, it is seen that the previously described passages 18, 19,20, 21 are in communication with annular chambers 38, 39, 40, 41,respectively, formed by opposed outwardly opening annular channels onthe outer surfaces of the diaphragms 22, 25, 28, and inwardly openingannular channels axially spaced along the bore 16 of the compressorcasing 7. These annular chambers 38-41, are sealed with respect to eachother by any appropriate means, for example, O-rings (not shown). Thediaphragms 22, 25, 28 are provided with integrally cast passages orexternally congurated surfaces cooperating with surfaces of adjacentdiaphragms to form passages for conducting air between the annularchambers 38-41 and respective ones of the shrouds inputs and diffuseroutputs.

In addition, the output from the last stage diffuser 30 is connected bythe diaphragms into the annular chamber 42 formed by opposed annularchannels in the diaphragm 25 and casing 7. From the annular chamber 42,the high pressure compressor output may pass upwardly, as shown in FIG.11, through an outlet 43 to the point of use, storage tank, conventionalblow-off device, or the like. Also, the compressor output may beconducted from the annular chamber 42 downwardly through outlet 44 intothe compressor base 1 to be connected to piping to the point of use and/or be connected to various pressure responsive control and monitoringdevices, which for example may have meters, warning lights or the likeon the control panel 45 as shown in FIG. 1. Also, in FIG. 1, the outlet43 is shown with a sealing plug or cap that is used when an excesspressure blow-off device is not employed and the compressor output isdirected downwardly into the compressor base for connection with pipingto the point of use. Further, the compressor output from annular chamber42 is conducted by means of a generally axially extending passage 46(FIG. 1l) that is cast into the casing 7, but not in communication withany of the previously described passages of the casing 7 except forthose shown in FIG. 1l. The passage 46 conducts a portion of thecompressor output to annular chamber 47, which is shown in FIG. 5 asbeing formed by opposed annular channels respectively in the casing 7and diffuser 22. From the annular chamber 47, the high pressurecompressor output is directed into an annular chamber 48 formed betweenthe shroud 23 and diaphragm 22. If desired, a nozzle may be insertedthrough the shroud 23 to direct the gases from chamber 48 against theblade tips of impeller 13 to produce a power recovery turbine action totake care of excess pressure on partial load. The structure and functionof this power recovery will not be described in detail, because it formsthe subject matter of one of the previously mentioned co-pendingapplications. For the purpose of this application, it is important thatthis capacity is built into the structure so that the chamber exists andif desired, appropriate pressure responsive valving may be incorporatedinto the passage 46 for dumping excess pressure into the annular chamber48, and the shroud 23 may be drilled for reception of one or morenozzles to complete the turbine. This capacity is built in whether usedor not.

From the above, it is seen that the compressor barrel assembly of thepresent invention may be removed from the one-piece cast casing forinspection, repair and replacement of the various individual uid guideelements, particularly, the diaphragms, shrouds and diffusers. Theconstruction of these elements as individual pieces greatly facilitatesthe casting of the internal piping, a reduction in manufacturing cost,ease of replacement, and ease of modifying for power recovery. Theseadvantages are gained without the heretofore correlated disadvantages oftolerance accumulation, thermal expansion problems and extremedifficulty with respect to sealing and alignment.

Since the diaphragms are the only axially clamped elements, tolerancesinvolved in the manufacture of the diffusers and shrouds will notcontribute in any accumulated tolerance error; further, thermalexpansion of the shrouds and diffusers will not be transferred throughthe diaphragms. Thermal expansion would otherwise be a particularproblem in view of the close proximity of the shrouds and diffusers tothe impellers, the difficulty of cooling the same, and the desirableconstruction of light weight material such as aluminum that has a highthermal expansion. These advantages are gained by mounting the diffusersand shrouds between the diaphragms with axial free play. The free playis taken up, particularly for starting purposes, by means of axiallycompressed O-rings, which further serve the function of sealing. Oncepressure has been built up in the compressor, the piston effectsheretofore mentioned will predominate to hold the diffusers and shroudstightly and sealingly in their proper positions. The piston effects willincrease proportionately with increased compressor pressures, to producea desired corresponding increase in sealing effect.

Accurate alignment is obtained by means of telescopically engagingannular surfaces between the casing, diaphragms, diffusers and shrouds.The cylindrical bore of the one piece casing forms the primary radialreference point, by providing engagement With the diaphragms and onepiece impeller mounting housing. The impeller has a thermal expansionreference point at its furtherest end provided by a thrust bearing, toprovide additional length for thermal expansion of the rotor assembly,which additional length will have a greater thermal expansion than thecorresponding relatively cool and massive casing 6, to compensate forthe rather high thermal expansion to be encountered with the aluminumdiaphragms, shrouds, and diflusers.

With interstage piping being integrally cast into the casing anddiaphragms, the size, complexity and cost of the compressor is greatlyreduced. Correspondingly, setup time, sealing problems and maintenanceare greatly reduced.

Although a preferred embodiment of the present invention has beenillustrated to show a specific advantageous form, further modifications,variations and embodiments are contemplated according to the broaderaspects of the present invention.

What is claimed is:

1. A pumping device, comprising: a casing; a rotor rotatably mounted insaid casing and having a plurality of centrifugal impellers; a pluralityof annular diaphragms axially stacked Within said casing correspondingin number and respectively surrounding said impellers; means clampingsaid diaphragms axially directly to each other; a plurality of separatestationary diffusers correspondingly associated with and correspondingin number to said impellers, means mounting said difusers to saiddiaphragms about their respective irnpellers with axial free play withrespect to said diaphragms; and resilient means axially biasing each ofsaid diffusers relative to said diaphragms whereby axial expansion ofsaid diffuser relative to said diaphragms will be absorbed.

2. The device of claim 1, wherein said axially biasing means include aplurality of sealing G-rings.

3. The device of claim 1, wherein said axially biasing means includingseparate piston means for each diffuser having at least one axial facesubjected to the iluid being pumped for producing a net axial forcebiasing its associated diffuser toward an adjacent diaphragm.

4. The device of claim 3, wherein said axially biasing means include aplurality of sealing O-rings.

5. The device of claim 1, constituting a multi-stage centrifugalcompressor wherein said casing is a one piece casting having an innercylindrical bore provided with a plurality of annular inwardly openingchannels in fluid communication with respective impellers; and saiddia-V phragms and casing having a plurality of integral passage meansfor conducting fluid out of the casing from each impeller and into saidcasing for at least some of said impellers.

6. The device of claim 1, including an end closure for one axial end ofsaid casing; bearing means providing the sole rotational support of saidrotor and being located solely on the side of said rotor with said endclosure; and means providing removal of said rotor, said diaphragms andsaid diifusers axially from said casing in the direction opposite fromsaid end closure.

7. The device of claim 6, wherein said end closure has an inwardlyfacing cylindrical surface and said casing has an inwardly facingcylindrical surface flush with and abutting said end closure cylindricalsurface; and one of said diaphragms having an outwardly facingcylindrical surface overlapping and engaging each of said end closureand casing cylindrical surfaces.

8. The device of claim 6, constituting a multi-stage centrifugalcompressor wherein there are three impellers on said rotor, with thefirst stage impeller having an inlet facing axially away from said endclosure, the second stage impeller having an inlet facing said endclosure, and the third stage impeller being located axially intermediatesaid first and second stage impellers and having an inlet facing awayfrom said end closure.

9. The device of claim 1, including means for holding said diaphragmsconcentric with respect to each other in said casing, includingcylindrical outer surfaces on said diaphragms in engagement with saidcasing, and telescopically interengaging cylindrical surfaces.

10. The device of claim 1, wherein said means clamping include an endclosure rigidly secured to said casing and a plurality of tension boltsaxially extending through said diaphragms and into said end closure.

11. A pumping device, comprising: a casing; a rotor rotatably mounted insaid casing and having a plurality of open centrifugal impellers; aplurality of annular diaphragms axially stacked Within said casingcorresponding in number and respectively surrounding said impellers;means clamping said diaphragms axially directly to each other; aplurality of stationary shrouds corresponding in number and respectivelyassociated with said impellers; at least one shroud and one diaphragmbeing provided with confronting surfaces arranged in spaced relation oneto another to define an axial clearance space and resilient means insaid clearance space biasing said shroud relative to said diaphragmwhereby engagement of parts in an axial direction is assured.

12. The device of claim 11, wherein said axial biasing means include aplurality of O-rings compressed in the axial direction between at leastsome of said shrouds and some of said diaphragms.

13. The device of claim 12, wherein said shrouds are piston means forproducing a net axial force, in the same direction as the force producedby said Oerings, from the pressurized -fluid during operation.

14. The device of claim 11, wherein said rotor includes only threecentrifugal impellers with the first stage impeller having its inletopening in one axial direction,

the second stage impeller having its inlet opening in they".

and the third stage shroud, the third stage diffuser, the

second stage diffuser and the second stage shroud being axially mounted,in order, between the third stage diaphragm and the second stagediaphragm.

15. The device of claim 14, wherein said rotor is overhung with bearingmeans at only one axial end.

16. A multi-stage pumping device for fluids, comprising: a cast onepiece casing having an inner cylindrical bore; a plurality of diaphragmscorresponding in number to the number of stages being received withinand engaging said bore in axial stacked relationship, each of saiddiaphragms being of a one piece casting; each of said diaphragms havingintegrally cast non-communicating passage means extending radiallycompletely therethrough and corresponding to at least a first stageOutlet passage, a second stage inlet passage, and a second stage outletpassage; and said casing having integrally cast non-com'- municatingpassage means extending radially therethrough respectively in -uidalignment with each of said diaphragm passage means.

17. The device of claim 16, wherein said diaphgragms have outwardlyopening annular chan-nels in respective communication with andcorresponding in number to said diaphragm passage means; and said casinghaving a plurality of inwardly opening channels radially oppositecorresponding ones of said diaphragms outwardly opening channels to formtherewith a plurality of annular uid chambers. 1

18. A centrifugal pumping device, comprising: an open centrifugalimpeller mounted for rotation about an axis; a separate stationaryshroud and a separate stationary diffuser operatively mounted about saidimpeller to form a single pumping stage; a first axial abutment; asecond axial abutment; at least one of said axial abutments beingprovided with a surface confronting a surface on at least one of saidstationary parts in spaced relation thereto to define an axial clearancespace; and an Oring sealingly and axially compressed between said oneaxial abutment and said one stationary part to provide means for axiallybiasing said diffuser and shroud axially toward said other axialabutment.

19. The device of claim 18, including piston means responsive to thepumped iluid to' produce a net axial force on said diffuser and shroudcomplementary to the axial force produced by said O-ring.

20. The device of claim 18, including a second open centrifugal impellerdrivingly secured to said first mentioned centrifugal impeller; a secondshroud and a second diffuser operatively associated with said secondimpeller and mounted in axial stacked relationship between one of saidaxial abutrnents and said first mentioned shroud and diffuser; and saidO-ring clamping all of said diffusers and shrouds in the axialdirection.

21. The device of claim 20, wherein said impellers have inlets openingin axially opposite directions away from each other; and said diffusersbeing axially between said shrouds.

22. The device of claim 21, including casing means operatively mountingsaid diffusers, shrouds and impellers for axial removal in the directionopposite from the direction of the axial force applied by said O-ring.

23. The device of claim 22, including an overhung rotor rigidly carryingsaid impellers and having bearing means only at its axial end oppositefrom said O-ring.

(References on following page) References Cited UNITED STATES PATENTSSalzer 415-106 Anderson 415-106 Sherwood et al. 4715-105 Brose 415-104MacMeeken 415-199 'Spillmann et a1 415-108 Howard 415-199 Holzhausen415-196 Hall 415-199 10 FOREIGN PATENTS 19,470 9/1906 Great Britain415-106 539,373 9/1941 Great Britain 415-199 R 964,020 5/1957 Germany415-199 1,029,676 5/1958 Germany 415-199 956,732 4/1964 Great Britain415-219 959,711 6/1964 Great Britain 415-219 U.S. C1. X.R.

